Polycrystalline Cu (InGa) Se2/CdS Thin Film Solar Cells Made by New Precursors

We report on the state of the art second-generation of solar cells, based on CuInGaSe2 thin film technology. These types of cells reached on the laboratory scale, photovoltaic energy conversion efficiencies of about 20,3%; this is the highest efficiency ever obtained for thin film solar cells. In particular, we describe the materials, the sequence of layers, the characteristic deposition techniques and the devices that are realized by adopting this semiconductor as an absorber material. Particular emphasis will be placed on major innovations developed in our laboratory, that have made it possible to achieve high efficiencies with polycrystalline materials, in addition to showing how the thin-film technology is mature enough to be easily transferred to industrial production. We will put in to evidence that our procedure is a completely dry process, which makes use only of the sputtering technique for the deposition of all the layers, including CdS, and the high temperature treatment in pure selenium for the selenization of the CuInGaSe2 film.